JP7620447B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device.

In order to assist the driver in driving operations, in addition to a normal mode in which the driving force of the vehicle is controlled in response to the driver's acceleration/deceleration operations (i.e., accelerator operation and brake operation), some vehicles can execute a constant speed control mode (e.g., cruise control mode). In the constant speed control mode, as disclosed in Patent Document 1, for example, constant speed control (e.g., cruise control) is executed to control the driving force of the vehicle without the driver's acceleration/deceleration operations so that the vehicle speed is maintained at a target vehicle speed.

JP 2008-221935 A

In the constant speed control mode, when the driver operates the accelerator, the constant speed control is interrupted and an override is executed to control the vehicle's driving force to a required driving force corresponding to the accelerator opening. Meanwhile, when the constant speed control mode is being executed and the vehicle is trying to go over a step on the road, the wheels may be pressed against the step and fail to climb over the step. In this case, the driver may operate the accelerator to make the vehicle go over the step, which may result in an override being executed. If the accelerator operation is released while the wheels are still failing to climb over the step, the override ends and the constant speed control resumes.

Here, the target driving force in constant speed control may be controlled by feedback control such as PID control. In this case, the target driving force in constant speed control may include an integral control component based on the integrated value of the deviation between the vehicle speed and the target vehicle speed. Conventionally, the integral control component of the target driving force was generally reset (i.e., became 0) when constant speed control was resumed. As a result, if the override ended while the wheels had failed to climb up a step and constant speed control was resumed, the vehicle's driving force would be insufficient, and there was a risk of the vehicle sliding down an uphill road, for example.

The present invention aims to provide a vehicle control device that can eliminate the lack of vehicle driving force after constant speed control is resumed after an override is performed in constant speed control mode.

In order to solve the above problem, a vehicle control device according to one embodiment of the present invention includes a control unit capable of switching between a normal mode in which the driving force of the vehicle is controlled in response to acceleration/deceleration operations by the driver, and a constant speed control mode in which the driving force of the vehicle is controlled without the driver's acceleration/deceleration operations so that the vehicle speed is maintained at a target vehicle speed, and in the constant speed control mode, the control unit calculates a target driving force using integral control based on an integrated value of the deviation between the vehicle speed and the target vehicle speed, and executes constant speed control to control the driving force of the vehicle to the target driving force, and if the required driving force corresponding to the accelerator opening of the vehicle exceeds the target driving force in the constant speed control during the execution of the constant speed control, the constant speed control is interrupted and an override is executed to control the driving force of the vehicle to the required driving force, and the override is ended and the constant speed control is resumed. If the wheels of the vehicle have failed to climb up the step when the constant speed control is resumed, the integral control component of the target driving force is set based on the required driving force during the execution of the override.

In the constant speed control mode, if the wheels of the vehicle have failed to climb the step when constant speed control is resumed, the control unit may set the integral control component of the target driving force to a value equivalent to the required driving force at the end of the override.

In the constant speed control mode, if the wheels of the vehicle fail to climb the step when constant speed control is resumed, the control unit may set the integral control component of the target driving force to a value equivalent to the maximum value of the required driving force while the override is being executed.

In the constant speed control mode, if the wheels of the vehicle have failed to climb a step when constant speed control is resumed, the control unit may set the integral control component of the target driving force based on the gradient of the road on which the vehicle is traveling, in addition to the required driving force during execution of the override.

The control unit can switch between a high-speed constant-speed control mode and a low-speed constant-speed control mode in which the target vehicle speed is set to a value lower than that in the high-speed constant-speed control mode, and in the low-speed constant-speed control mode, when the constant-speed control is resumed, if the vehicle's wheels have failed to climb up the step, the control unit can set the integral control component of the target driving force based on the required driving force during the execution of the override.

The present invention makes it possible to eliminate the lack of vehicle driving force when constant speed control is resumed after an override is performed in constant speed control mode.

1 is a schematic diagram showing a schematic configuration of a vehicle on which a control device according to an embodiment of the present invention is mounted; FIG. 2 is a block diagram showing an example of a functional configuration of a control device according to an embodiment of the present invention. 5 is a flowchart showing an example of a process flow relating to driving force control performed by a control unit during execution of a constant speed control mode according to the embodiment of the present invention. 7A and 7B are diagrams illustrating an example of transitions of various state quantities during execution of a constant speed control mode according to a comparative example. FIG. 4 is a diagram showing an example of transitions of various state quantities during execution of a constant speed control mode according to the embodiment of the present invention. 6 is a diagram showing an example of transitions of various state quantities during execution of a constant speed control mode according to an embodiment of the present invention, different from the example of FIG. 5 . 7 is a diagram showing an example of transition of various state quantities during execution of a constant speed control mode according to the embodiment of the present invention, different from the examples of FIGS. 5 and 6 . FIG.

The preferred embodiment of the present invention will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific values shown in the embodiment are merely examples to facilitate understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid duplicated explanations, and elements not directly related to the present invention are not illustrated.

<Vehicle configuration>
The configuration of a vehicle 1 equipped with a control device 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

Figure 1 is a schematic diagram showing the general configuration of vehicle 1. In Figure 1, vehicle 1 is shown with the forward movement direction of vehicle 1 defined as the forward direction, the backward movement direction opposite to the forward movement direction defined as the rearward direction, and the left and right sides when facing forward defined as the left and right directions, respectively.

Vehicle 1 is an electric vehicle that has a drive motor (specifically, front-wheel drive motor 15f and rear-wheel drive motor 15r in FIG. 1) as a drive source and runs using the power output from the drive motor.

Note that the vehicle 1 described below is merely one example of a vehicle in which the control device according to the present invention is installed, and as described below, the configuration of a vehicle in which the control device according to the present invention is installed is not particularly limited to the configuration of vehicle 1.

As shown in FIG. 1, the vehicle 1 includes front wheels 11a, 11b, rear wheels 11c, 11d, a front differential 13f, a rear differential 13r, a front-wheel drive motor 15f, a rear-wheel drive motor 15r, an inverter 17f, an inverter 17r, a battery 19, a control device 100, an accelerator opening sensor 201, a brake sensor 203, a front-wheel motor rotation speed sensor 205f, and a rear-wheel motor rotation speed sensor 205r.

Hereinafter, when there is no distinction between the front wheels 11a, 11b, rear wheels 11c, and rear wheels 11d, they will also be referred to simply as wheels 11. When there is no distinction between the front wheel drive motor 15f and the rear wheel drive motor 15r, they will also be referred to simply as drive motor 15. When there is no distinction between the inverter 17f and the inverter 17r, they will also be referred to simply as inverter 17. When there is no distinction between the front wheel motor rotation speed sensor 205f and the rear wheel motor rotation speed sensor 205r, they will also be referred to simply as motor rotation speed sensor 205.

The front wheel drive motor 15f is a drive motor that outputs power to drive the front wheels 11a and 11b. The front wheel 11a corresponds to the left front wheel, and the front wheel 11b corresponds to the right front wheel.

Specifically, the front-wheel drive motor 15f is driven using power supplied from the battery 19. The front-wheel drive motor 15f is connected to the front differential device 13f. The front differential device 13f is connected to the front wheels 11a, 11b via drive shafts. The power output from the front-wheel drive motor 15f is transmitted to the front differential device 13f, and then distributed and transmitted to the front wheels 11a, 11b by the front differential device 13f.

The front-wheel drive motor 15f is, for example, a multi-phase AC motor, and is connected to the battery 19 via an inverter 17f. The DC power supplied from the battery 19 is converted to AC power by the inverter 17f and supplied to the front-wheel drive motor 15f.

In addition to outputting power to drive the front wheels 11a, 11b, the front-wheel drive motor 15f also functions as a generator that generates electricity using the kinetic energy of the front wheels 11a, 11b. When the front-wheel drive motor 15f functions as a generator, electricity is generated by the front-wheel drive motor 15f and a braking force is applied to the vehicle 1 through regenerative braking. The AC power generated by the front-wheel drive motor 15f is converted to DC power by the inverter 17f and supplied to the battery 19. This charges the battery 19.

The rear wheel drive motor 15r is a drive motor that outputs power to drive the rear wheels 11c and 11d. The rear wheel 11c corresponds to the left rear wheel, and the rear wheel 11d corresponds to the right rear wheel.

Specifically, the rear-wheel drive motor 15r is driven by power supplied from the battery 19. The rear-wheel drive motor 15r is connected to the rear differential device 13r. The rear differential device 13r is connected to the rear wheels 11c, 11d via drive shafts. The power output from the rear-wheel drive motor 15r is transmitted to the rear differential device 13r, and then distributed and transmitted to the rear wheels 11c, 11d by the rear differential device 13r.

The rear wheel drive motor 15r is, for example, a polyphase AC motor, and is connected to the battery 19 via an inverter 17r. The DC power supplied from the battery 19 is converted to AC power by the inverter 17r and supplied to the rear wheel drive motor 15r.

In addition to outputting power to drive the rear wheels 11c, 11d, the rear-wheel drive motor 15r also functions as a generator that generates electricity using the kinetic energy of the rear wheels 11c, 11d. When the rear-wheel drive motor 15r functions as a generator, electricity is generated by the rear-wheel drive motor 15r and a braking force is applied to the vehicle 1 through regenerative braking. The AC power generated by the rear-wheel drive motor 15r is converted to DC power by the inverter 17r and supplied to the battery 19. This charges the battery 19.

The accelerator opening sensor 201 detects the accelerator opening, which is the amount of accelerator pedal operation by the driver, and outputs the detection result.

The brake sensor 203 detects the amount of brake operation, which is the amount of brake pedal operation by the driver, and outputs the detection result.

The front wheel motor rotation speed sensor 205f detects the rotation speed of the front wheel drive motor 15f and outputs the detection result. The rear wheel motor rotation speed sensor 205r detects the rotation speed of the rear wheel drive motor 15r and outputs the detection result. The detection result of the motor rotation speed sensor 205 is used in the processing performed by the control device 100 as information indicating the rotation speed of the power transmission shaft of the vehicle 1 (specifically, the shaft included in the power transmission system between the drive motor 15 and the wheels 11).

The control device 100 includes a CPU (Central Processing Unit), which is an arithmetic processing device; a ROM (Read Only Memory), which is a storage element that stores programs and calculation parameters used by the CPU; and a RAM (Random Access Memory), which is a storage element that temporarily stores parameters that change as appropriate during CPU execution.

The control device 100 communicates with each device mounted on the vehicle 1 (e.g., the inverter 17, the accelerator opening sensor 201, the brake sensor 203, and the motor rotation speed sensor 205). The communication between the control device 100 and each device is realized, for example, by using CAN (Controller Area Network) communication.

Figure 2 is a block diagram showing an example of the functional configuration of the control device 100.

For example, as shown in FIG. 2, the control device 100 has an identification unit 110 and a control unit 120.

The determination unit 110 determines the vehicle speed of the vehicle 1 (hereinafter, simply referred to as the vehicle speed) based on the rotation speed of the power transmission shaft of the vehicle 1. Information indicating the vehicle speed determined by the determination unit 110 is output to the control unit 120 and is used in the processing performed by the control unit 120.

Specifically, the identification unit 110 identifies the vehicle speed based on the detection result of the motor rotation speed sensor 205. In identifying the vehicle speed, the detection results of both the front wheel motor rotation speed sensor 205f and the rear wheel motor rotation speed sensor 205r may be used, or only one of the detection results of the front wheel motor rotation speed sensor 205f and the rear wheel motor rotation speed sensor 205r may be used. In identifying the vehicle speed, information other than the detection result of the motor rotation speed sensor 205 (for example, information indicating the rotation speed of a drive shaft connecting the wheels 11 and the differential device) may be used as information indicating the rotation speed of the power transmission shaft of the vehicle 1.

The control unit 120 controls the operation of each device in the vehicle 1, thereby controlling the running of the vehicle 1. For example, the control unit 120 includes a determination unit 121 and a motor control unit 122.

The determination unit 121 performs various determinations using information transmitted from each device in the vehicle 1 to the control device 100. The determination results by the determination unit 121 are used for various processes performed by the control unit 120.

The motor control unit 122 controls the operation of each drive motor 15 by controlling the operation of each inverter 17. Specifically, the motor control unit 122 controls the operation of the switching element of the inverter 17f to control the supply of power between the battery 19 and the front-wheel drive motor 15f. This allows the motor control unit 122 to control the generation and power generation of power by the front-wheel drive motor 15f. The motor control unit 122 also controls the operation of the switching element of the inverter 17r to control the supply of power between the battery 19 and the rear-wheel drive motor 15r. This allows the motor control unit 122 to control the generation and power generation of power by the rear-wheel drive motor 15r.

When driving the drive motors 15 to provide the vehicle 1 with a driving force, the motor control unit 122 may drive both the front wheel drive motor 15f and the rear wheel drive motor 15r, or may drive only one of the front wheel drive motor 15f and the rear wheel drive motor 15r. When both the front wheel drive motor 15f and the rear wheel drive motor 15r are driven, the distribution of the driving force of each drive motor 15 may be set appropriately. The motor control unit 122 can control the driving force of the vehicle 1 (i.e., the driving force provided to the vehicle 1) by controlling the driving force of each drive motor 15.

Here, the control unit 120 can switch between a normal mode and a constant speed control mode as the driving mode of the vehicle 1. The normal mode is a driving mode in which the driving force of the vehicle 1 is controlled according to the acceleration/deceleration operation (i.e., accelerator operation and brake operation) by the driver. The constant speed control mode is a driving mode in which the driving force of the vehicle 1 is controlled without depending on the acceleration/deceleration operation by the driver so that the vehicle speed of the vehicle 1 is maintained at a target vehicle speed. The constant speed control mode is sometimes called a cruise control mode.

Furthermore, the control unit 120 can switch between a high-speed constant-speed control mode and a low-speed constant-speed control mode as the constant-speed control mode. The high-speed constant-speed control mode may be called a high-speed cruise control mode, and the low-speed constant-speed control mode may be called a low-speed cruise control mode. In the low-speed constant-speed control mode, the target vehicle speed is set to a value lower than that in the high-speed constant-speed control mode. For example, the target vehicle speed in the high-speed constant-speed control mode is set to a speed within a range of 20 km/h to 115 km/h, and the target vehicle speed in the low-speed constant-speed control mode is set to a speed within a range of 2 km/h to 15 km/h. The target vehicle speed in the constant-speed control mode can be adjusted, for example, by an input operation by the driver.

For example, the vehicle 1 is provided with an input device (e.g., a switch or button) for selecting which driving mode to execute among the normal mode, the high-speed constant speed control mode, and the low-speed constant speed control mode, and the driver can select the driving mode by operating the input device. The control unit 120 executes the driving mode selected by the driver. Note that if the driver performs a specific operation such as braking while the constant speed control mode is being executed, the control unit 120 stops the constant speed control mode and switches to the normal mode.

In normal mode, the control unit 120 controls the operation of the drive motor 15 so that the driving force of the vehicle 1 corresponds to the accelerator opening. This allows the driving force of the vehicle 1 to be controlled in response to the accelerator operation by the driver. The control unit 120 also controls the operation of a brake device, such as a hydraulic brake device, mounted on the vehicle 1 so that the braking force applied to the vehicle 1 corresponds to the amount of brake operation. This allows the braking force applied to the vehicle 1 to be controlled in response to the brake operation by the driver.

In the constant speed control mode, the control unit 120 calculates a target driving force so that the vehicle speed approaches the target vehicle speed, and controls the driving force of the vehicle 1 to the target driving force. For example, the control unit 120 calculates the target driving force using feedforward control based on the vehicle speed and feedback control (e.g., PID control) based on the deviation between the vehicle speed and the target vehicle speed. In this case, the calculated target driving force Fc is expressed, for example, by the following formula (1).

Fc=Ff+Fp+Fi+Fd...(1)

In formula (1), Ff indicates a feedforward control component based on the vehicle speed, Fp indicates a proportional control component based on the deviation between the vehicle speed and the target vehicle speed (i.e., P component), Fi indicates an integral control component based on the integrated value of the deviation (i.e., I component), and Fd indicates a differential control component based on the differential value of the deviation (i.e., D component). The driving force Fp of the P component is specifically obtained by multiplying the deviation by a gain. The driving force Fi of the I component is specifically obtained by multiplying the integrated value of the deviation by a gain. The driving force Fd of the D component is specifically obtained by multiplying the differential value of the deviation by a gain. The driving force Ff of the feedforward control component corresponds to a driving force estimated to be required to maintain the vehicle speed at the target vehicle speed when the vehicle 1 is traveling on a flat road. Note that a flat road means a road on which the absolute value of the gradient (i.e., the inclination with respect to the horizontal direction in the traveling direction of the vehicle 1) is equal to or less than a predetermined value.

The method of calculating the target driving force Fc of the driving motor 15 is not limited to the example in which it is calculated using formula (1). For example, the feedforward control may be omitted from the above example (i.e., the driving force Ff may be omitted from formula (1)), and the PID control may be replaced with PI control (i.e., the driving force Fd may be omitted from formula (1)).

The functions of the control device 100 according to this embodiment may be partially divided among multiple control devices, or multiple functions may be realized by one control device. When the functions of the control device 100 are partially divided among multiple control devices, the multiple control devices may be connected to each other via a communication bus such as a CAN.

As described above, the control unit 120 of the control device 100 can execute a constant speed control mode in which the driving force of the vehicle 1 is controlled without the driver's acceleration/deceleration operation so that the vehicle speed is maintained at the target vehicle speed. Here, when the driver operates the accelerator during execution of the constant speed control mode, the control unit 120 can interrupt the constant speed control and execute an override in which the driving force of the vehicle 1 is controlled to the required driving force corresponding to the accelerator opening. In this embodiment, by devising the driving force control at the time of resuming the constant speed control when the override is ended and the constant speed control is resumed, it is possible to eliminate the shortage of driving force of the vehicle 1 after the constant speed control is resumed after the override is executed in the constant speed control mode. Details of the processing related to the driving force control performed by the control unit 120 during execution of the constant speed control mode will be described later.

<Control device operation>
Next, the operation of the control device 100 according to the embodiment of the present invention will be described with reference to FIGS.

Figure 3 is a flowchart showing an example of the process flow related to the drive force control performed by the control unit 120 while the constant speed control mode is being executed. The control flow shown in Figure 3 is started when the constant speed control is being executed in the constant speed control mode, and is started repeatedly after the constant speed control ends.

As described later, according to the control flow shown in FIG. 3, when the constant speed control is resumed after the override ends while the wheel 11 has failed to climb the step, the lack of driving force of the vehicle 1 can be suppressed. Here, the lower the target vehicle speed in the constant speed control mode, the more likely it is that the actual vehicle speed is insufficient for the vehicle speed required to make the wheel 11 climb the step, and the more likely it is that the wheel 11 will fail to climb the step. Therefore, in the low-speed constant speed control mode, the wheel 11 is more likely to fail to climb the step compared to the high-speed constant speed control mode. Therefore, it is preferable that the control unit 120 executes the control flow shown in FIG. 3 below, particularly while the low-speed constant speed control mode is being executed. However, the control unit 120 may execute the control flow shown in FIG. 3 below while the high-speed constant speed control mode is being executed.

When the control flow shown in FIG. 3 is started, first, in step S101, the judgment unit 121 judges whether or not the override start condition is satisfied. The override start condition is that the required driving force corresponding to the accelerator opening of the vehicle 1 exceeds the target driving force in the constant speed control. The required driving force is the driving force requested by the driver by operating the accelerator. In other words, when the start condition is satisfied, the driver wishes to interrupt the constant speed control and increase the driving force of the vehicle 1.

If the determination in step S101 is NO (i.e., if it is determined that the override start condition is not satisfied), the control flow shown in FIG. 3 ends. On the other hand, if the determination in step S101 is YES (i.e., if it is determined that the override start condition is satisfied), the process proceeds to step S102, where the motor control unit 122 interrupts constant speed control. Then, following step S102, in step S103, the motor control unit 122 starts an override. In the override, the motor control unit 122 controls the driving force of the vehicle 1 to a required driving force corresponding to the accelerator opening.

After step S103, in step S104, the determination unit 121 determines whether or not an override end condition has been satisfied. The override end condition is, for example, that the accelerator operation by the driver has been released. For example, the determination unit 121 can determine that the accelerator operation has been released when the required driving force becomes smaller than the target driving force at the time when the constant speed control was interrupted.

If the result of step S104 is NO (i.e., if it is determined that the override termination condition is not satisfied), the determination process of step S104 is repeated. On the other hand, if the result of step S104 is YES (i.e., if it is determined that the override termination condition is satisfied), the process proceeds to step S105, where the motor control unit 122 ends the override.

After step S105, in step S106, the determination unit 121 determines whether the wheel 11 has failed to climb the step. The failure of the wheel 11 to climb the step occurs when the wheel 11 is pressed against the step when the vehicle 1 is attempting to pass over the step. Here, the step may be a strip-shaped protruding portion on the road surface (e.g., a speed bump, etc.) or a joint between road surfaces with a difference in height (e.g., a joint between a roadway and a sidewalk, etc.). Regardless of the type of step, the wheel 11 may be pressed against the step and fail to climb the step.

In step S106, the determination unit 121 determines whether the wheel 11 has failed to climb the step, for example, based on the driving state of the drive motor 15 and the vehicle speed of the vehicle 1. For example, the determination unit 121 determines that the wheel 11 has failed to climb the step if the state in which the vehicle speed is maintained below a threshold value (for example, a value close to 0 km/h) continues for a reference time or more even though the drive motor 15 is being driven and a driving force is being generated in the vehicle 1. The reference time is set to an appropriate time at which it can be determined that there is no prospect of resolving the state in which the vehicle speed is maintained below the threshold value even though a driving force is being generated in the vehicle 1.

If the answer is YES in step S106 (i.e., if it is determined that the wheel 11 has failed to climb the step), in step S107, the motor control unit 122 sets the I component of the target driving force for constant speed control (i.e., the integral control component) based on the required driving force during execution of the override. Specifically, the motor control unit 122 sets the integrated value of the deviation in the integral control so that the I component of the target driving force corresponds to the required driving force during execution of the override.

By setting the I component of the target driving force as described above, when constant speed control is resumed after the override ends while the wheel 11 has failed to climb the step, the I component of the target driving force is not reset (i.e., it is not set to 0) and becomes a value corresponding to the required driving force during the execution of the override. This eliminates the shortage of driving force of the vehicle 1 after the constant speed control is resumed, and for example, prevents the vehicle 1 from sliding down an uphill road. Details of the process of setting the integrated value based on the required driving force during the execution of the override will be described later with reference to Figures 5 to 7.

If the result of the determination in step S106 is NO (i.e., if it is not determined that the wheel 11 has failed to climb the step), the process proceeds to step S108, where the motor control unit 122 resets the I component of the target driving force of the constant speed control (i.e., sets it to 0). Specifically, the motor control unit 122 resets the I component by resetting the integrated value of the deviation in the integral control. When the constant speed control is resumed after the override is ended in a state in which the wheel 11 has not failed to climb the step (for example, the wheel 11 has successfully climbed the step), it is preferable to reset the I component in this manner in order to suppress sudden acceleration of the vehicle 1. For example, the vehicle 1 may be traveling on an uphill road during the execution of the override, but may have entered a flat road when the override is ended. In such a case, if the I component is not reset, the vehicle 1 may suddenly accelerate.

After step S107 or step S108, the process proceeds to step S109, where the motor control unit 122 resumes constant speed control, and the control flow shown in FIG. 3 ends.

Now, with reference to Figures 4 and 5, we will explain the differences between the constant speed control mode of the comparative example and the constant speed control mode of this embodiment.

Figure 4 is a diagram showing an example of the transitions of various state quantities during execution of the constant speed control mode according to the comparative example. In Figure 4, the transitions of the various state quantities are shown as vehicle speed [km/h], step climbing failure flag, accelerator opening [%] override flag, actual driving force [N], constant speed control target driving force [N], and required driving force [N]. The actual driving force [N] refers to the driving force actually applied to the vehicle 1. Note that the D component of the constant speed control target driving force is omitted from the illustration.

The step climbing failure flag is set to 1 when it is determined that the wheel 11 has failed to climb the step, and is set to 0 when it is determined that the wheel 11 has not failed to climb the step. The override flag is set to 1 when an override is being executed, and is set to 0 when an override is not being executed. Each of the above flags is stored, for example, in a memory element of the control device 100, and is rewritten by the control unit 120.

In the example shown in FIG. 4, before time T1, the vehicle 1 is traveling uphill with constant speed control being executed in constant speed control mode. Then, at time T1, the wheel 11 hits a step and fails to climb the step. The vehicle speed starts to decrease from time T1, and reaches 0 km/h at time T2. In this way, as a result of the wheel 11 failing to climb the step, the step climbing failure flag switches from 0 to 1 at time T3 after time T2.

After time T2 when the vehicle speed becomes 0 km/h, the P component of the target driving force of the constant speed control increases, and the actual driving force also increases. However, after time T2, the state in which the wheels 11 fail to climb the step is maintained. Now, at time T4 after time T3, the driver operates the accelerator. Therefore, at time T4, the accelerator opening increases, and the required driving force also increases. Then, the constant speed control is interrupted and an override is executed, triggered by the required driving force exceeding the target driving force. Therefore, at time T4, the override flag switches from 0 to 1. After time T4, the actual driving force is controlled to the required driving force.

At time T5, which is after time T4, the driver releases the accelerator pedal. Therefore, at time T5, the accelerator opening decreases to 0, and the required driving force also decreases to 0. The release of the driver's accelerator pedal triggers the end of the override and the resumption of constant speed control. Therefore, at time T5, the override flag switches from 1 to 0.

In the comparative example, at time T5, when the override is ended and the constant speed control is resumed, the I component of the target driving force of the constant speed control is reset to 0 regardless of whether the wheel 11 has failed to climb the step. After time T5, the I component of the target driving force increases from 0. Here, the I component changes slowly because it is calculated based on the integrated value of the deviation between the vehicle speed and the target vehicle speed. Therefore, after time T5, the target driving force of the constant speed control increases slowly from 0. As a result, after time T5, the actual driving force becomes insufficient, and the vehicle 1 skids. In the example of FIG. 4, after time T5, the vehicle speed takes a negative value, and the vehicle 1 moves backward.

Figure 5 is a diagram showing an example of the transition of various state quantities during execution of the constant speed control mode according to this embodiment. Each of the state quantities shown in Figure 5 is the same as that in Figure 4.

As described above, in this embodiment, when the wheel 11 has failed to climb the step when the constant speed control is resumed after the override is ended, the control unit 120 sets the I component (i.e., the integral control component) of the target driving force of the constant speed control based on the required driving force during the execution of the override, based on the required driving force during the execution of the override. In the example of FIG. 5, since it is determined that the wheel 11 has failed to climb the step at time T5 when the constant speed control is resumed, unlike the example of FIG. 4, the I component of the target driving force of the constant speed control is not reset (i.e., it is not set to 0) and becomes a value corresponding to the required driving force during the execution of the override between time T4 and time T5.

In the example of FIG. 5, the required driving force is approximately constant between time T4 and time T5. In the graph of the target driving force in FIG. 5, the required driving force between time T4 and time T5 is indicated by a two-dot chain line L1. For example, at time T5, when constant speed control is resumed, the control unit 120 sets the I component of the target driving force of the constant speed control to match the required driving force between time T4 and time T5. However, at time T5, the control unit 120 may also set the I component of the target driving force to a value obtained by adding or subtracting a predetermined adjustment value to the required driving force between time T4 and time T5.

As described above, in the example of FIG. 5, at time T5, when constant speed control is resumed after the override ends with the wheel 11 having failed to climb the step, the I component of the target driving force of the constant speed control becomes the required driving force between time T4 and time T5. Therefore, after time T5, the target driving force of the constant speed control increases from the required driving force between time T4 and time T5. As a result, after time T5, the shortage of actual driving force is resolved and the vehicle 1 is prevented from rolling downhill. In the example of FIG. 5, after time T5, the vehicle speed is maintained at 0 km/h and the vehicle 1 does not roll back.

In the example of FIG. 5 described above, the required driving force is approximately constant while an override is being executed. However, the required driving force may change while an override is being executed. Below, an example in which the required driving force changes while an override is being executed will be described with reference to FIG. 6 and FIG. 7.

Figure 6 is a diagram showing an example of the transition of various state quantities during execution of the constant speed control mode according to this embodiment, which is different from the example shown in Figure 5. Each of the state quantities shown in Figure 6 is the same as those in Figures 4 and 5.

In the example of FIG. 6, unlike the example of FIG. 5, the required driving force changes between time T4 and time T5 while the override is being performed. Specifically, the required driving force increases from time T4 to time T6, reaches a maximum at time T6, and then decreases from time T6 to time T5. In the graph of the target driving force in FIG. 6, the required driving force between time T4 and time T5 is indicated by the two-dot chain line L2.

In the example of FIG. 6, at time T5 when constant speed control is resumed, the control unit 120 sets the I component of the target driving force of the constant speed control to a value equivalent to the required driving force at time T5 when the override ends. For example, at time T5, the control unit 120 sets the I component of the target driving force of the constant speed control to match the required driving force at time T5 when the override ends. This prevents the driver from feeling uncomfortable due to a large change in the driving force applied to the vehicle 1 after the constant speed control is resumed. However, at time T5, the control unit 120 may set the I component of the target driving force to a value obtained by adding or subtracting a predetermined adjustment value to the required driving force at time T5 when the override ends.

Figure 7 is a diagram showing an example of the progression of various state quantities during execution of the constant speed control mode according to this embodiment, which is different from the examples in Figures 5 and 6. Each of the state quantities shown in Figure 7 is the same as in Figures 4 to 6. In the example of Figure 7, the required driving force changes in the same way as in the example of Figure 6 between time T4 and time T5 during execution of the override.

In the example of FIG. 7, at time T5 when the constant speed control is resumed, the control unit 120 sets the I component of the target driving force of the constant speed control to a value equivalent to the maximum value of the required driving force between time T4 and time T5 when the override is being performed (i.e., the required driving force at time T6). For example, the control unit 120 sets the I component of the target driving force of the constant speed control at time T5 to match the required driving force at time T6. This more effectively resolves the shortage of driving force of the vehicle 1 after the constant speed control is resumed. Therefore, for example, it is possible to more reliably prevent the vehicle 1 from rolling down an uphill road and to quickly overcome a step. However, the control unit 120 may set the I component of the target driving force at time T5 to a value obtained by adding or subtracting a predetermined adjustment value to the required driving force at time T6.

Here, in the constant speed control mode, if the wheel 11 has failed to climb up the step when the constant speed control is resumed, the control unit 120 may set the I component of the target driving force based on other parameters in addition to the required driving force during the execution of the override. For example, the other parameters may include the gradient of the road on which the vehicle 1 is traveling. Note that the gradient of the road may be obtained, for example, from the detection results of a sensor that detects the acceleration of the vehicle 1, or from map data, etc.

When the road slopes vertically upward relative to the traveling direction (i.e., when the road is an uphill road), there is a strong need to increase the I component of the target driving force in order to more reliably prevent the vehicle 1 from sliding downhill after constant speed control is resumed, and also to quickly overcome the step. On the other hand, when the road slopes vertically downward relative to the traveling direction (i.e., when the road is a downhill road), there is a strong need to bring the I component of the target driving force closer to the required driving force at the end of the override in order to prevent the driver from feeling uncomfortable due to a large change in the driving force applied to the vehicle 1 after constant speed control is resumed.

Therefore, for example, when the constant speed control is resumed and the wheel 11 has failed to climb the step, if the road is an uphill road, the control unit 120 may set the I component of the target driving force to a value equivalent to the maximum value of the required driving force while the override is being executed. On the other hand, when the constant speed control is resumed and the wheel 11 has failed to climb the step, if the road is a downhill road, the control unit 120 may set the I component of the target driving force to a value equivalent to the required driving force at the end of the override.

The control unit 120 may change the set value of the I component of the target driving force in accordance with the gradient of the road when the road is an uphill road. Similarly, the control unit 120 may change the set value of the I component of the target driving force in accordance with the gradient of the road when the road is a downhill road.

<Effects of the control device>
Next, the effects of the control device 100 according to the embodiment of the present invention will be described.

In the control device 100 according to this embodiment, when the wheel 11 fails to climb the step when the constant speed control is resumed after the override is ended, the control unit 120 sets the I component (i.e., the integral control component) of the target driving force of the constant speed control based on the required driving force during the execution of the override. As a result, when the constant speed control is resumed when the override is ended in a state in which the wheel 11 fails to climb the step, the I component of the target driving force is not reset (i.e., it does not become 0) and becomes a value corresponding to the required driving force during the execution of the override. Therefore, the shortage of the driving force of the vehicle 1 after the constant speed control is resumed is eliminated. As a result, for example, the vehicle 1 is prevented from sliding down an uphill road. Also, for example, even on a downhill road, the driving force of the vehicle 1 is greatly insufficient with respect to the driving force required to achieve the climb over the step is eliminated.

In addition, in the control device 100 according to this embodiment, in the constant speed control mode, if the wheel 11 has failed to climb the step when the constant speed control is resumed, the control unit 120 preferably sets the I component of the target driving force to a value equivalent to the required driving force at the end of the override. This prevents the driver from feeling uncomfortable due to a large change in the driving force applied to the vehicle 1 after the constant speed control is resumed.

In addition, in the control device 100 according to this embodiment, in the constant speed control mode, if the wheel 11 has failed to climb over the step when the constant speed control is resumed, the control unit 120 preferably sets the I component of the target driving force to a value equivalent to the maximum value of the required driving force while the override is being executed. This more effectively resolves the shortage of driving force of the vehicle 1 after the constant speed control is resumed. Therefore, for example, it is possible to more reliably prevent the vehicle 1 from rolling down an uphill road, and furthermore to quickly achieve climbing over the step.

In addition, in the control device 100 according to this embodiment, in the constant speed control mode, if the wheel 11 has failed to climb the step when the constant speed control is resumed, the control unit 120 preferably sets the I component of the target driving force based on the gradient of the road on which the vehicle 1 is traveling, in addition to the requested driving force during the execution of the override. This makes it possible to more appropriately set the I component of the target driving force based on the gradient of the road when the constant speed control is resumed in the case where the override has ended with the wheel 11 having failed to climb the step.

In addition, in the control device 100 according to this embodiment, in the low-speed constant speed control mode, if the wheel 11 has failed to climb up the step when constant speed control is resumed, the control unit 120 preferably sets the I component of the target driving force based on the required driving force during execution of the override. As described above, in the low-speed constant speed control mode, the wheel 11 is more likely to fail to climb up the step than in the high-speed constant speed control mode. Therefore, it is possible to effectively utilize the effect of eliminating the shortage of driving force of the vehicle 1 after constant speed control is resumed.

The above describes a preferred embodiment of the present invention with reference to the attached drawings, but it goes without saying that the present invention is not limited to the above-mentioned embodiment, and various modifications and alterations within the scope of the claims also fall within the technical scope of the present invention.

For example, in the above, vehicle 1 is described as an electric vehicle equipped with a front-wheel drive motor 15f and a rear-wheel drive motor 15r as drive sources, but the configuration of a vehicle equipped with a control device according to the present invention is not particularly limited to vehicle 1. For example, a vehicle equipped with a control device according to the present invention may be an electric vehicle in which a drive motor is provided for each wheel (i.e., equipped with four drive motors), or a hybrid vehicle equipped with a drive motor and an engine as drive sources. Also, for example, a vehicle equipped with a control device according to the present invention may be a vehicle in which components have been added, modified, or removed from vehicle 1 described with reference to FIG. 1.

In addition, for example, the processes described in this specification using flowcharts do not necessarily have to be performed in the order shown in the flowcharts. In addition, additional processing steps may be employed, and some processing steps may be omitted.

1 Vehicles 11a, 11b Front wheels (wheels)
11c, 11d Rear wheel (wheel)
13f Front differential device 13r Rear differential device 15f Front wheel drive motor 15r Rear wheel drive motor 17f Inverter 17r Inverter 19 Battery 100 Control device 110 Identification unit 120 Control unit 121 Determination unit 122 Motor control unit 201 Accelerator opening sensor 203 Brake sensor 205f Front wheel motor rotation speed sensor 205r Rear wheel motor rotation speed sensor

Claims (5)

a control unit capable of switching between a normal mode in which a driving force of the vehicle is controlled in response to an acceleration/deceleration operation by a driver and a constant speed control mode in which a driving force of the vehicle is controlled without the acceleration/deceleration operation by the driver so that the vehicle speed of the vehicle is maintained at a target vehicle speed;
In the constant speed control mode, the control unit
a constant speed control for controlling the driving force of the vehicle to the target driving force by calculating a target driving force using integral control based on an integrated value of the deviation between the vehicle speed and the target vehicle speed;
When a required driving force corresponding to an accelerator opening of the vehicle exceeds the target driving force in the constant speed control during execution of the constant speed control, the constant speed control is interrupted and an override is executed to control the driving force of the vehicle to the required driving force;
when the wheels of the vehicle have failed to climb up a step at the time of resuming the constant speed control by terminating the override, a component of the integral control of the target driving force is set based on the required driving force during the execution of the override.
Vehicle control device. When the wheels of the vehicle have failed to climb up a step when the constant speed control is resumed in the constant speed control mode, the control unit sets a component of the integral control of the target driving force to a value equivalent to the required driving force at the end of the override.
The vehicle control device according to claim 1 . the control unit, in the constant speed control mode, when the wheels of the vehicle have failed to climb up a step upon resumption of the constant speed control, sets the integral control component of the target driving force to a value equivalent to a maximum value of the required driving force during execution of the override.
The vehicle control device according to claim 1 or 2. When the wheels of the vehicle have failed to climb up a step when the constant speed control is resumed in the constant speed control mode, the control unit sets the integral control component of the target driving force based on a gradient of a road on which the vehicle is traveling in addition to the required driving force during the execution of the override.
The vehicle control device according to any one of claims 1 to 3. The control unit is
The constant speed control mode can be switched between a high-speed constant speed control mode and a low-speed constant speed control mode in which the target vehicle speed is set to a value lower than that in the high-speed constant speed control mode,
in the low-speed constant speed control mode, when the wheels of the vehicle have failed to climb up a step upon resumption of the constant speed control, a component of the integral control of the target driving force is set based on the required driving force during execution of the override.
The vehicle control device according to any one of claims 1 to 4.

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